WO02/068205, WO02/074548, WO2004/043704 and WO2005/012442, and also US2003/0186000, US2003/0186001, US2005/0032957 and US2006/0040217 (the content of each of which is incorporated herein by reference), describe laser imaging and also materials that can be used for that purpose. Examples that are provided typically involve the use of high energy lasers.
There are many attractions in using non-contact near-IR sources, in particular diode lasers, to generate images from coatings for applications such as variable information packaging. Favourable attributes of diode lasers such as economy, portability and ease of use, are attractive for current needs in the packaging industry, such as in-store labelling.
The use of ink formulations that incorporate materials which absorb radiation from far-IR to mid-IR sources such as heat (˜1 to 20 μm) and CO2 laser (˜10 μm), allows the production of coatings that can generate a distinct coloured image on exposure to such wavelengths but not near-IR sources. The use of ink formulations that incorporate materials which absorb radiation from near-IR sources, such as diode lasers (˜1 μm), allows the production of coatings that will generate a distinct coloured image on exposure to near, mid or far-IR irradiation.